Síntese e caracterização de carreadores de oxigênio para combustão com recirculação química obtidos via reação de combustão assistida por microondas

Perovskites oxides win importance by its properties and commercials applications, they have a high thermal stability, have conductive properties, electrical, catalytic, electro catalytic, optical and magnetic, and are thermally stable. Because of these properties, are being widely studied as carriers of oxygen in the process of power generation with CO2 capture. In this work, the base carrier system La1-xMexNiO3 (Me = Ca and Sr) were synthesized by the method via the combustion reaction assisted by microwave. were synthesized from the combustion reaction method by microwave process. This method control the synthesi`s conditions to obtain materials with specific characteristics. The carriers calcined at 800 ° C/2h were analyzed by thermal analysis (TG-DTA), to verify its thermal stability, X-ray diffraction (XRD) to verify the phase formation, with subsequent refinement by the Rietveld method, to quantify the percentage of phases formed, the surface area by BET method was determined, scanning electron microscopy (SEM) was obtained to evaluate the material morphology and temperature programmed reduction (TPR) was done to observe the metallic phase of the nickel. After all proposed characterization and analysis of their results can be inferred to these oxides, key features so that they can be applied as carriers for combustion reactions in chemical cycles. The final products showed perovskite-type structures K2NiF4 (main) and ABO3.

Obtenção e caracterização físico-química de blendas poliméricas, baseadas em POE e PMMA, dopadas com dióxido de titânio

The study of polymer blends has been an alternative method in the search field of new materials for obtaining materials with improved properties. In this work blends of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) doped with titanium dioxide (TiO2) were studied. The PEO is a polymer semicrystalline structure varying between, 70 and 84% crystallinity, while the PMMA exhibits behavior amorphous in their structure. The use of TiO2 is related to corrosion-resistant of titanium as well as good heat transfer and other characteristics. The study of these polymer blends doped TiO2 gives the properties junction organic (polymer) and inorganic (oxide) which leads to modification of the properties of the resultant material. The blends were doped TiO2 (POE/PMMA/TiO2) in different proportions of the PMMA with the PEO and TiO2 fixed. The ratios were: 90/10/0,1; 85/15/0, 1; 80/20/0,1, 75/25/0,1 and 70/30/0,1. The resulting material was obtained in powder form and being characterized by Fourier Transformed Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Electrochemical Impedance Spectroscopy (EIS). The infrared spectra (IR) for the blends in different ratios showed a band at 1744 cm-1, characteristic of the C=O stretching, which increases in intensity with increasing PMMA composition, while in the spectrum of pure PEO this band is absent. This may suggest that the interaction is occurring between the polymers. In the micrographs of the blends also observed change in their surfaces with variation of the composition of PMMA, contributing to the change of the electrical properties of the material. The EIS data showed that the material exhibited conductivity of the order of 10-6 S.cm-1. The blend in the ratio B2(85/15/0, 1) showed better conductivity, σ = 1.56 x 10-6 S.cm-1. It was observed that the diffusion coefficient for the blends, B5(70/30/0, 1) was the largest, 1.07 x 10-6 m2.s-1. The XRD data showing that, with the variation in the composition of the PMMA blend crystallinity of the material is decreased reaching a minimum B3(80/20/0,1), and then increases again. Thermal analysis suggests that blends made from the material obtained can be applied at room temperature

A energia e suas implicações no ensino-aprendizagem da química

The area of Education in Chemistry in Brazil has appeared over 30 years and its growth has been accelerated by the need of comprehension of the processes of teaching and learning in chemistry. Many researches, in this area, has among its investigation objects the teaching tools like teaching materials and the learning processes of students in high school and basic education, but when dealing with higher levels of education, they are seldom portrayed. This study aimed to investigate the General Chemistry textbooks with respect to approach the concept of energy; know the main ideas of graduate students in Chemistry on the relation of the concept of energy and chemical transformations; finally, developing a cicle of studies with the proposition of an approach wich inter-relate the concept of energy and its implications in the teaching-learning process of a chemical transformation. To do so, we used as instruments a questionnaire, press conference, conceptual map and experimental activities. All activities of the study cicle were videotaped and recorded, transcribed and the results organized in tables. For the activities of the study cicle texts that have been developed and inter-relating concepts of chemistry and energy, which in turn gave theoretical support to the activities in the cycle. In the analysis it was used as a theoretical content the analysis of Laurence Bardin. The results revealed that the analysis of the book might be perceived that not always the concept of energy is used in order to generate the abstract thought of chemical transformations, but that the main macroscopic thermodynamic variables are present in the explanation of these transformations. During the study cicle, were studied two chemical reactions: the first one, made possible to approach the macroscopic dimension to quantify the concept of energy and the second one, made possible to demonstrate the macro and microscopic dimension of the concept of energy during a chemical transformation. In all reactions proposed, students used, in most of the times, as explanations, only macroscopic observations of the reactions under study and failed to realize that the concept of energy can be used to explain macro and microscopic chemical transformation. As a final action of the study cicle, students requested further discussion, to clarify the link between the concept of energy and the meanings constructed in the process of studying the reactions. This is done through an oral explanation, during the cycle, and registered in this thesis and attempts to show the interrelationship existing conceptual

Carregadores de oxigênio a base de níquel suportado em materiais mesooros para aplicação na recirculação química com reforma (RQR)

Oxygen carriers are metal oxides which have the ability to oxidize and reduce easily by various cycles. Due to this property these materials are widely usedin Chemical-Looping Reforming processes to produce H2 and syngas. In this work supports based on MCM-41 and La-SiO2 were synthesized by hydrothermal method. After the synthesis step they were calcined at 550°C for 2 hours and characterized by TG, XRD, surface area using the BET method and FTIR spectroscopy. The deposition of active phase, in this case Nickel, took place in the proportions of 5, 10 and 20% by weight of metallic nickel, for use as oxygen carriers.The XRD showed that increasing in the content of Ni supported on MCM-41 resulted in a decrease in spatial structure and lattice parameter of the material. The adsorption and desorption curves of the MCM-41 samples exhibited variations with the increase of Ni deposited. Surface area, average pore diameter and wall density of silica showed significant changes , due to the increase of the active phase on the mesoporous material. By other hand, in the samples with La-SiO2 composition was not observed peaks characteristic of hexagonal structure, in the XRD diffractogram. The adsorption/desorption isotherms of nitrogen observed are type IV, characteristic of mesoporous materials. The catalytic test indicates that the supports have no influence in the process, but the nickel concentration is very important, because the results for minor concentration of nickel are not good. The ratio H2/O2 was close to 2, for all 15 cycles involving the test storage capacity of O2, indicating that the materials are effective for oxygen transport

Análise das avaliações realizadas na disciplina de arquitetura atômica e molecular no curso de química, modalidade a distância da UFRN

The field of education is very rich and allows us to research in various aspects. The area of chemical education has been growing more and more, and an important aspect that has been researching this area is about the learning difficulties of students. The approach of the themes atomic structure and chemical bonds are developed in high school and have many problems that are often brought to higher education becoming an obstacle to the advancement of learning. It is necessary for these initial themes - the atomic structure and chemical bonds - are well understood by the student to the other contents of Chemistry will be understood more easily. This paper aims to describe, analyze errors and difficulties presented in the assessments of the discipline Atomic and Molecular Architecture, the students of the degree course in Chemistry - EAD, with respect to the contents of " Atomic Structure and Chemical Bonding ", by of the assessments made by the students and the Virtual Learning Environment (VLE), taking into account the activities , discussion forum and access to materials . AVA allows obtaining reports which were used to analyze regarding access / participation to assess their contribution to learning and its relation to the final result (pass / fail). It was observed that the most frequent errors in the assessments are related to the early part of the chemistry that is the understanding of atomic structure and evolution models. Students who accessed the extra material and participated in the activities and forums were students who achieved success in the course. Ie, the difficulties were emerging and the use of available teaching strategies, students could minimize such difficulties, making their performance in activities and assessments were better. Was also observed by attending the AVA, the discipline began with a large withdrawal from the page access as well as the frequency of face- evidence from observation in Listing presence of classroom assessments

Reciclagem química de Polietileno utilizando Sílica Mesoporosa tipo SBA-15 avalizada por Termogravimetriae Espectrometria de Massas

The chemical recycling of polyolefins has been the focus of increasing attention owing potential application as a fuel and as source chemicals. The use of plastic waste contributes to the solution of pollution problems.The use of catalysts can enhance the thermal degradation of synthetic polymers, which may be avaliated by Themogravimetry (TG) and mass spectrometry (MS) combined techniques. This work aims to propose alternatives to the chemistry recycling of low-density polyethylene (LDPE) on mesoporous silica type SBA-15 and AlSBA-15.The mesoporous materials type SBA-15 and AlSBA-15 were synthesized through the hydrothermal method starting from TEOS, pseudobohemite, cloridric acid HCl and water. As structure template was used Pluronic P123. The syntheses were accomplished during the period of three days. The best calcination conditions for removal of the organic template (P123) were optimized by thermal analysis (TG/DTG) and through analyses of Xray diffraction (XRD), infrared spectroscopy (FT-IR), nitrogen adsorption and scanning electron microscopy (SEM) was verified that as much the hydrothermal synthesis method as the calcination by TG were promising for the production of mesoporous materials with high degree of hexagonal ordination. The general analysis of the method of Analog Scan was performed at 10oC/min to 500 oC to avoid deterioration of capillary with very high temperatures. Thus, with the results, we observed signs mass/charge more evident and, using the MID method, was obtained curve of evolution of these signals. The addition of catalysis produced a decrease in temperature of polymer degradation proportional to the acidity of the catalyst. The results showed that the mesoporous materials contributed to the formation of compounds of lower molecular weight and higher value in the process of catalytic degradation of LDPE, representing an alternative to chemical recycling of solid waste

Desenvolvimento de uma rota química alternativa de síntese de SrCo0,8Fe0,2O3- e LaNi0,3Co0,7O3- para aplicação na reação de oxidação do CO

This thesis focuses on the coprecipitation synthesis method for preparation of ceramic materials with perovskite structure, their characterization and application as catalytic material in the reaction of converting CO to CO2 developing a methodological alternative route of synthesis from the middle via oxalate coprecipitation material SrCo0,8Fe0,2O3-d. In order to check the influence of this method, it was also synthesized using a combined citrate - EDTA complexing method. The material was characterized by: X-ray diffraction (XRD), Rietveld refinement method, thermogravimetry and differential thermo analysis (TG / DTA), scanning (SEM) and transmission (TEM) electron microscopy, particle size distribution and surface analysis method BET. Both methods led to post-phase synthesis, with pH as a relevant parameter. The synthesis based on the method via oxalate coprecipitation among particles led to the crystalline phase as those obtained using a combined citrate - EDTA complexing method under the same conditions of heat treatment. The nature of the reagent used via oxalate coprecipitation method produced a material with approximately 80 % lower than the average size of crystallites. Moreover, the via oxalate coprecipitation method precursors obtained in the solid state at low temperature (~ 26 oC), shorter synthesis, greater thermal stability and a higher yield of around 90-95 %, maintaining the same order of magnitude the crystallite size that the combined citrate - EDTA complexing method. For purposes of comparing the catalytic properties of the material was also synthesized by the using a combined citrate - EDTA complexing method. The evaluation of catalytic materials SrCo0,8Fe0,2O3-d LaNi0,3Co0,7O3-d was accompanied on the oxidation of CO to CO2 using a stainless steel tubular reactor in the temperature range of 75-300 oC. The conversion CO gas was evaluated in both materials on the results shaved that the firm conversion was loves for the material LaNi0,3Co0,7O3-d

Transportadores sólidos de oxigênio à base de níquel e cobre suportados em aluminatos para combustão do metano pela tecnologia de recirculação química

In recent years, solid carriers suitable oxygen have been developed for use in different chemical processes recirculation. The success of this technology is directly related to the chemical reactivity and the oxygen storage capacity of the carrier. Thus, research into the development of new materials that can be applied to the process becomes extremely important. Possible candidates are the carriers based on nickel and copper for presenting favorable thermodynamic properties. In this work, aluminates type MAl2O4 (M = Mg and Ca) and M0,9B0,1Al2O4 (B = Ni and Cu) that are used as supports were synthesized by combustion reactions assisted by microwave and calcined at 900°C/2h. Then, the carriers were impregnated with 10% (m/m) of nickel or copper, and subsequently calcined at 600°C/2h to obtain the solid oxygen carriers, which were characterized by X-ray diffraction (XRD) Microscopy scanning electron microscopy (SEM) and temperature programmed reduction (TPR). Reactions simulating the combustion process by chemical recirculation were performed by cycles reduction/oxidation, in order to evaluate the reactivity of carriers. XRD analysis revealed diffraction peaks of the spinel type structures. In the doped substrates were verified the presence of secondary phases, suggesting that all the metal was incorporated into the spinel structure. In solid oxygen carriers, the NiO and CuO phases were observed after impregnation of active phases on different media. The results of evaluations of chemical cycles reduction/oxidation revealed that TSO's impregnated with nickel in various media were more active and are potential candidates for use in the chemical recirculation technology

Possibilidades de enfoque CTS para o ensino superior de química: proposta de uma abordagem para ácidos e bases

Scientific education has been passing by redefinitions, contestations and new contributions from the research on science teaching. One contribution is the idea of science and technology literacy, allowing the citizens not only knowing science but also understand aspects on the construction and motivation of scientific and technological research. In accordance with this idea, there is the Science-Technology-Society (STS) studies which, since the 1970s, has been contributing for science teaching and learning according to the comprehension of the relationships with society in the Western countries of the North. In Brazil, this approach began to gain projection from the 1990s when the first essays on the theme were published. Currently, there is a clear influence of this approach on the national curriculum guidelines, especially for the area of Natural Sciences, and also on the textbooks chosen by the High School National Program (Programa Nacional do Ensino Médio). However, there seems to be a gap in relation to the discussion on the specific curricular component seen in college on this approach. Thus, this study aims at adopting the approach STS, face to the preparation of complimentary educational material on acid and bases concepts studied in the course of General Chemistry of the Natural Sciences graduation program. To this end, it was performed a bibliographical research aiming at making the state-of-the-art in in these concepts in specific literature to science teaching. It is divided in two stages: systematic study (with sixteen journals chosen according to Qualis-Capes and an unsystematic study with direct search in databases and references in the papers of the systematic study. The studies had their content analyzed and the categories chosen a priori were the level of education, the acid-base theory adopted, and the strategy/theoretical frame of reference adopted. A second stage aimed at identifying attitudes and beliefs on STS (Science-Technology-Society) and CSE (Chemistry-Society-Environment) of students in the teacher and technologist training course in three diferent institutions: UTFPR, UFRN and IFRN. In this study, it was used two questionnaires, composed of a Likert scale, semantic differential scale and open questions. The quantitative data reliability was estimated through Cronbach’s alpha method, and tha data were treated according to classic statistics, using the mean as the centrality measures, and the mean deviation as dispersion. The qualitative data were treated according to the content analysis with categories taken from the reading of answers. In the third stage, it was analyzed the presence of STS and CSE content in chapters on acid and bases concepts of nine General Chemistry textbooks, frequently used in graduation programs in public institutions of the state of Rio Grande do Norte. The results showed that there are few proposals of acid and bases teaching, and they are generally aimed at High School or at instrumentation for teaching courses, and no course for General Chemistry. The student’s attitudes and beliefs show the presence of a positivist point of view based on the concept of Science and Technology neutrality and the salvation of its mediation. The books analysis showed just a few content on STS and CSE are found in the studied chapters, and they are generally presented disjointedly in relation to the rest of the main text. In the end, as suggestion to solve the absence of proposals STS in General Chemistry books, as well as the student’s positivist attitudes, it was developed some educational material to be used in the course of General Chemistry at College. The material is structured to introduce a historical view of the concepts preparation, present the use of materials, the industrial and technological processes, and social and environmental consequences of this activities

Síntese e caracterização de pigmentos nanométricos encapsulados pelos métodos dos precursores poliméricos, hidrotermal de microondas e co-precipitação associado à química sol-gel convencional

The demand for materials with high consistency obtained at relatively low temperatures has been leveraging the search for chemical processes substituents of the conventional ceramic method. This paper aims to obtain nanosized pigments encapsulated (core-shell) the basis of TiO2 doped with transition metals (Fe, Co, Ni, Al) through three (3) methods of synthesis: polymeric precursors (Pechini); hydrothermal microwave, and co-precipitation associated with the sol-gel chemistry. The study was motivated by the simplicity, speed and low power consumption characteristic of these methods. Systems costs are affordable because they allow achieving good control of microstructure, combined with high purity, controlled stoichiometric phases and allowing to obtain particles of nanometer size. The physical, chemical, morphological, structural and optical properties of the materials obtained were analyzed using different techniques for materials characterization. The powder pigments were tested in discoloration and degradation using a photoreactor through the solution of Remazol yellow dye gold (NNI), such as filtration, resulting in a separation of solution and the filter pigments available for further UV-Vis measurements . Different calcination temperatures taken after obtaining the post, the different methods were: 400 º C and 1000 º C. Using a fixed concentration of 10% (Fe, Al, Ni, Co) mass relative to the mass of titanium technologically and economically enabling the study. By transmission electron microscopy (TEM) technique was possible to analyze and confirm the structural formation nanosized particles of encapsulated pigment, TiO2 having the diameter of 20 nm to 100 nm, and thickness of coated layer of Fe, Ni and Co between 2 nm and 10 nm. The method of synthesis more efficient has been studied in the work co-precipitation associated with sol-gel chemistry, in which the best results were achieved without the need for the obtainment of powders the calcination process

Aplicação da perlita expandida modificada com ortofenantrolina na remoção do negro de eriocromo T em águas residuais geradas em laboratórios de ensino de química

In this study, we carried out the study of Eriochrome black T removal using expanded perlite modified orthophenanthroline by adsorption technique. The study of the adsorption process was performed by investigating the effect of the initial dye concentration, contact time and pH range of the solution (acidic and alkaline) in the adsorption process, for a so-called synthetic effluent (aqueous solution of black eriochrome T) and a real effluent (generated from the test for determining the water hardness, by complexation titration). The materials were characterized by Thermogravimetry / Differential Thermal Analysis (TG / DTA), absorption spectroscopy in the infrared (IR), X-ray Diffraction (XRD) and scanning electron microscopy (SEM). By analysis of XRD observed thinking on orthophenanthroline the modified expanded perlite. And by IR analysis showed an increase in intensity and a detailed enlargement of the absorption band related to the axial deformation of the OH bond of silanol groups of perlite (Si-OH). In the equilibration time of the study, in the evaluated time range (5-230 min) was not possible to observe the existence of a balance of time, probably attributed to the type of interaction between the Eriochrome black-T and the expanded perlite modified orthophenanthroline, being an interaction of surface origin. In the study effect of the initial concentration of the adsorbate in the case 2,0x10-4 mol / L natural pH (pH 5) gave the highest removal percentage value of eriochrome T black color with 63.74 % removal in 20 minutes of contact. In evaluating the effect of varying the pH of Eriochrome black T solution in the adsorption process, it was found that the more acidic the environment, the greater the percentage stain removal, being a result of acid-base interaction between the adsorbate and the adsorbent. In T Eriochrome black removal study in real effluent we used the optimized conditions by studying with synthetic sewage. The dye removal at pH 10, natural pH of the effluent was no significant reaching the maximum amount of color removal percentage of 8.12%, obtained already at pH 3 with maximum color removal 100.00% of color, once more proving that eriochrome black T and effectively interact better with the adsorbent at acid pH values (pH 5 or 3), and most efficiently at pH 3. thus one can mention that the perlite expanded (an amorphous aluminosilicate naturally acid) modified with orthophenanthroline (one Bronsted base) consists of a master and effective removal of coloring material in the acid-type aqueous solution, the conditions expressed in this study, can be applied as an adsorbent of this dye also mums real effluent.

Química em cena: uma proposta para formação inicial de professores de química

In educational observed difficulty in train teachers to meet the medium and higher education needs, and one reason for this is the different experiences in the training of educators in relation to those found in the classroom. So often arise criticisms related to relevance and efficiency of degree courses, as regards the performance of its natural mission, which weakens the teacher training. Thus, improving the quality of education is very dependent on the initiatives of teachers, creating teaching alternatives to strengthen their performance in school. From this reflection, it is concluded that teacher training needs new educational proposals that qualify, and so can promote the formation of his students more adequately. Among the educational proposals as alternatives to initial teacher training may use the scientific theater (TC). Considering this possibility, this work has been proposed as investigate and discuss the influence of TC combined with experimentation in the initial training of future teachers in Chemistry who participate in the Groups Fanatics chemistry Theatre (UERN) and Chemistry on Stage (UFRN). Therefore, there was, in a first stage, theatrical essays based on the theater of the oppressed, and written dramaturgical scripts, a collaborative proposal. To incorporate experimentation in chemistry to theater rehearsals, there was a systematic literature search and after content analysis, were selected categories, materials and reagents easily accessible, easy procedures and implementation with low risk of accidents and easy care chemical waste. In the second part we identified: a) the beliefs of student teachers in the use of TC ally trial for initial training of chemistry teachers; b) the influence of TC ally to trial on learning of chemical concepts of high school students who attended the shows; c) the reasons for using or not TC ally to trial by chemistry teachers who participated in the TC group and currently work in the classroom. In this study, questionnaires and interviews were used, compounds, respectively, by a Likert scale and open questions. Quantitative data were analyzed by classical statistics the media, using as centrality measures the average, the concordance argument and the average deviation. Qualitative data were discussed according to content analysis, with categories that emerged from reading the answers. These analyzes concluded that the licensees have a positive view on the use of scientific theater for disclosure of the chemical for use in the learning of chemical concepts, pedagogical and disciplinary knowledge, and to form promotion strategy for research and extension at the University. They credit improvements in their initial training on the use of scientific theater combined with experimentation. The TC provides motivation for the construction of conceptual thinking in an informal way of chemical communication, allowing the student to expand their knowledge, not only favoring the phenomenological approach, but also the construction of chemical knowledge and the internalization of scientific concepts.